Cross correlation functions for satellite scintillations at spaced receivers, show a systematic skewness, indicative of dispersive motions of ionospheric irregularities. Other features of the correlation functions, such as secondary pumps frequently present at large time lags and a very obvious change in the shape of the curve over a long baseline are also suggestive of dispersive ionospheric wave motions. The fact that the skewness is found to be greater for a low elevation satellite than for one at higher elevation, suggests that these motions might contain a frequency dependent vertical component. The effects of a vertical velocity component upon the conventional horizontal spaced receiver measurements are carefully analyzed. Useful information, relating to velocity dispersion, was also obtained at a single location, by investigating the correlation between multi-frequency scintillation records of a radio star. Because of previous suggestions that apparent skewness of spaced receiver correlation functions was due merely to statistical sampling errors, the stationarity of the scintillation data is examined in considerable detail.